1. Field of the Invention
The invention relates to a production method for producing unadulterated water samples when drilling a well and also relates to a device for implementing the method.
2. Description of the Prior Art
In the method according to the invention, water samples originating in a water-conducting horizontal approached by the bore are taken from contaminated soil. The samples are free of contamination which can enter the water samples by pumping the samples through the hollow bar and the bore as soon as the samples have left the water-conducting horizontal. Such contamination is generally based on elements of the bore rinse which has absorbed stagnant water from the surrounding rock or previously drilled water-conducting horizontals and, therefore, contains adulterating substances such as contamination when drilling in contaminated soil. The method according to the invention makes it possible to suppress such contamination in the sampled water and, therefore, to analyze which water qualities can be expected for which samples.
This is based primarily on the largely ring-shaped filter sand body, through which the water sample is pumped, deposited in the circular space between the boring bar and the bore before each sample is taken. The top section of the sand filter body, which surrounds a nonperforated conduit in the hollow bar, traps solid matter in the rinse and is compressed, forming a natural ring seal against the water-conducting horizontal in which the perforated bar conduit is positioned. In the method according to the invention, the described filter sand body is incorporated into the system after a period of time when pumping the water sample out of the bore, until the above-mentioned ring seal is formed and clear water flows from the approached horizontal. In doing this, the filter sand is restrained by the bar.
The principle of this method is already known from PCT application WO 82/04,352. If several groundwater horizontals lying above one another are to be tested according to this method, the bar has a large number of perforated bar conduits which are positioned according to the distance of the water-conducting layers and are each fitted with a collecting mechanism for closing off the bore wall. These mechanisms are extended when the bar is lifted and restrain the deposited filter sand so that the above-mentioned ring-shaped filter sand bodies can be formed.
This previously known method can normally be implemented with only two bars which must be inserted alternately or sequentially into the bore. The bar necessary for taking samples has a relatively complex structure and requires knowledge of the distance between the water-conducting horizontals in order to arrange the perforated bar conduits at the correct intervals for producing the filter sand bodies. According to this method, the well bore is, in general, partially or fully drilled and the bar containing the perforated bar conduits subsequently inserted. For organizational reasons, this is quite disadvantageous and easily produces incorrect results if one must drill in unknown soil and does not know how deep the bore must be drilled in order to strike a water-conducting horizontal which will supply water of a suitable quality and quantity.
The invention is based on the goal of implementing the previously known method so as to eliminate the need to change the bars between water samples, yet still obtain unadulterated water samples.